Segment-type grinding ring



Filed Dec. 7, 1965 Jan. 30, 1968 F. M. BARTON 3,366,338

SEGMENT-TYPE GRINDING RING 2 Sheets-Sheet 1 INVENTOR. FRANK M. BAR TON BY WM Zn.

ATTORNEY F. M. BARTON 3,366,338

SEGMENT-TYPE GRINDING RING I Jan. 30, 1968 2 Sheets-Sheet Filed Dec. 7, 1965 Fig.3

INVENTOR.

FRANK MBARTO'N Mal/7. 75m

ATTORNEY United States Patent 3,366,338 SEGMENT-TYPE GRINDING RING Francis M. Barton, Parsippany, N.J., assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed Dec. 7, 1965, Ser. No. 512,086 6 Claims. (Cl. 241-47) This invention relates to pulverizing apparatus, and particularly to improvements in pulverizing apparatus of the ring and roll type.

In this type of apparatus, the grinding elements of the mill comprise a grinding ring, which is fitted to'a grinding table, and a plurality of grinding rolls or balls adapted to travel on the grinding ring, preferably in a race in the latter. Grinding loads are applied to the rolls or balls by means of a coil spring assembly or similar arrangement resulting in crushing or pulverizing of materials such as coal between the grinding elements.

As a result of the pulverizing action, the grinding elements of the pulverizer are subject to considerable wear, which in the course of time, requires replacement. Because of economic considerations, and because the size of pulverizers in general, and coal pulverizers in particular, has been increasing in recent years, the replacement of the grinding elements and particularly the grinding ring has become a major problem. This is primarily due to the physical dimensions and weight of the components.

This becomes more apparent when it is considered that a single piece grinding ring for a large pulverizer of fifty (50) or more tons per hour grinding capability will have an outside diameter in the order of ten feet and a weight in the order of eight (8) to nine (9) tons. The removal and handling of such a mass of metal requires substantial dismantling of the pulverizer, special handling equipment, and a relatively long period of shut-down for the pulverizer and its associated equipment. All of the foregoing adds up to increasing maintenance cost as mill sizes become larger.

As an additional consideration, casting or forging of the large grinding rings presents problems in fabrication, also due to the weights and dimensions involved. As mill sizes increase, it becomes increasingly difficult to obtain castings or forgings of satisfactory quality, frequently increasing capital costs which must be passed on to the consumer.

Accordingly, it is an object of the present invention to overcome the above disadvantages, and in particular to provide a pulverizing unit requiring lower replacement and maintenance costs, lower initial capital costs, and having improved quality.

In accordance with these objects, the invention comprises in combination a mill table which has an upper surface and an annular shaped seat arranged in the upper surface, and a grinding ring disposed in the seat comprising a plurality of side-by-side segments which define the ring, and also define a grinding race. The segments and the table seat are provided with complementary inside edges adjacent the table axis which are angled upwardly and inwardly to permit upward withdrawal of the segments from the table seat and complementary outside edges similarly angled with the seat outside edge overhanging the outside segment edges to restrict said upward withdrawal. The seat angled inside and outside edges are slightly further apart than the segment corresponding angled edges to permit slight radial movement or play of the segments in the seat, and wedge blocks are removably secured to the table adjacent the seat inside edge adapted to force the segments during normal operation radially outward against and beneath the seat outside edge. The table further comprises at least one "ice removable plate member secured to the table defining a portion of the seat outside edge coextensive with at least one segment to permit radial withdrawal of one segment on removal of the plate.

When usual wear demands replacement of the grinding ring, it is a simple matter to remove the wedge block and plate member and radially withdraw one of the ring segments. This permits some side-to-side movement in the other ring segments so that they can be worked free of the seat outside edge holding them in place, and withdrawn upwardly from the table seat.

The invention and advantages will become apparent upon consideration of the following description with reference to the accompanying drawings in which:

FIGURE 1 is a cross section view of a ring-roll mill embodying the invention;

FIGURE 2 is a section view taken along line 22 of FIG. 1;

FIGURE 3 is a section view taken along line 3-3 of FIG. 1;

FIGURE 4 is a top plan view of a segment in accordance with the invention; and

FIGURE 5 is a section view taken along line 5-5 of FIG. 4.

Referring to the drawings, the mill 10, FIG. 1, comprises a grinding table 12 which is adapted to rotate driven by a suitable constant speed motor broadly indicated by the numeral 14 through a suitable reduction gear or like arrangement. The grinding elements of the mill comprise a grinding ring, generally indicated by the numeral 16, fitted to the grinding table, and, inthis example, three grinding rolls 18. Grinding loads are applied to the rolls by means of coil springs 20 between a spring ring 22 which is stationary relative the table and a thrust ring 24 which is in contact with the grinding rolls and spaced from the table by the rolls.

In operation, the grinding rolls 18 are frictionally driven by the grinding ring 16 and travel in an upper track formed by the thrust ring 24 and race 28 defined by the grinding ring. As a result, a planetary motion of the rolls occurs with the rolls revolving about their own axes as they simultaneously revolve about the table axis at a translational speed approximately half that of the table.

A spider type guide assembly 30 is provided to space the rolls about the table.

Coal to be pulverized enters the mill through the centrally located feed pipe 32 and drops down on to the slowly rotating grinding table where it is carried by centrifugal force to the grinding ring and is crushed between the grinding ring and grinding rolls. The pulverized coal forms a definite bed of partially ground material above the airport ring 34 surrounding the table, the flow of air through the ring carrying the pulverized material upwardly out of the mill. The height of the bed varies with the rate of feed and the air flow quantity.

Referring to all of the figures, the grinding ring 16 com-prises a plurality of pie-shaped segments 36, each segment being provided with an upper transverse grooved surface defining the table grinding race 28. The segments are identical in shape and are each provided with indentations 38 on the underside cooperating with keys 40 in the mill table seat to prevent undue side-by-side movement of the segments relative the table. The inner edges 42 of the ring segments slope upwardly and inwardly relative the axis of the mill table cooperating with the seat inside surface 44 of the table which is similarly sloped. The outer edges 46 of the ring segments are also angled inwardly and upwardly with the table seat having a similarly sloped outside edge 48 defining a slot in which the segments when forced outwardly are engaged.

This forcing of the segments is accomplished by means of an annular wedge 50 secured to the table by means of bolts 52, and having V-shaped surfaces 54 engaging and between corresponding segment and table surfaces 56 and 58. Turning down on the bolts 52 draws the wedge to the table upper surface forcing the segments outwardly and radially against the locking slot of the table (defined by surface 48). A clearance or gap and smaller dimensions of the segments relative the table seat permit this movement, so that the ring segments can simply be dropped vertically downward into the table seat and then forced outwardly into locking position.

Part of the table locking edge, which is the seat outside edge 48, is composed of a plate member 60 fastened to the periphery of the table which plate member circumferentially is coextensive with at least one of the segments. To remove one of the segments, it is a simple matter to unbolt the plate member, take it off the table, and radially withdraw the segment retained by the plate -member. In removal'of the segments for replacement,

the wedge is first removed, permitting the segment being withdrawn radially to ride over the key 40 for the segment. Following this, the remaining segments can be jostled sideways to free them from the table and then are lifted in an inwardly upwardly direction from the table until free of the seat inside locking edge.

Further to avoid obstruction in removing the segments from the table, the airport ring 34 is segmented so that one or more portions of the ring may be removed prior to radial withdrawal of one of the segments.

Although the invention has been described with reference to a specific embodiment, many variations within the spirit and scope of the following claims will be apparent to those skilled in the art.

What is. claimed is:

1. A grinding mill comprising a mill table including an upper surface and an annular shaped seat arranged therein; a plurality of side-by-side segments defining a grinding race disposed in the seat;

the segments and table seat including complementary inside edges adjacent the table axis angled upwardly and inwardly to permit upward withdrawal of the segments fro-m the table seat and complementary outer edges similarly angled with the seat edge overhanging the segment edges to restrict withdrawal, the seat angled edges being further apart than the segment angled edges to permit radial movement of the segments in the seat;

wedge block means removably secured to the table adjacent the inner edges thereof adapted to force the segments during normal operation radially outward against the seat outer edge;

the table further including at least one removable plate member secured to the table defining a portion of the seat outer edge coextensive with at least one segment to permit radial removal of the segment on removal of the plate. 4 v

2. A grinding mill according to claim 1 including key means in the table seat and segments to prevent annular movement of the segments relative the seat.

3. A grinding mill according to claim 2 wherein the wedge block means is an annular ring bolted to the table top, having a cross sectional area in the shape of'a trapezoid narrowmost at the bottom, the mill including complementary segment and table surfaces cooperating with the ring non-parallel sides whereby downward movement of the ring effects an outward radial movement of the mill segments.

4. A grinding mill according to claim 3 wherein the plate member is bolted to the mill table.

5. A grinding mill according to claim 4 wherein the side-by-side segments are pie-shaped, symmetrical and identical in design.

6. A grinding mill according to claim 5 including an air ring encompassing the grinding table through which air flows upwardly to entrain pulverized material therein, the air ring being segmented with portions removable to permit radial removal of one of the segments.

References Cited UNITED STATES PATENTS 2,879,006 3/1959 Clements et a1. 241-119 XR 3,199,794 8/1965 Poole 241117 XR 3,199,797 8/ 1965 Eft et a1 2411l9 XR WILLIAM W. DYER, JR., Primary Examiner.

W. D. BRAY, Assistant Examiner. 

1. A GRINDING MILL COMPRISING A MILL TABLE INCLUDING AN UPPER SURFACE AND AN ANNULAR SHAPED SEAT ARRANGED THEREIN; A PLURALITY OF SIDE-BY-SIDE SEGMENTS DEFINING A GRINDING RACE DISPOSED IN THE SEAT; THE SEGMENTS AND TABLE SEAT INCLUDING COMPLEMENTARY INSIDE EDGES ADJACENT THE TABLE AXIS ANGLED UPWARDLY AND INWARDLY TO PERMIT UPWARD WITHDRAWAL OF THE SEGMENTS FROM THE TABLE SEAT AND COMPLEMENTARY OUTER EDGES SIMILARLY ANGLED WITH THE SEAT EDGE OVERHANGING THE SEGMENT EDGES TO RESTRICT WITHDRAWAL, THE SEAT ANGLED EDGES BEING FURTHER APART THAN THE SEGMENT ANGLED EDGES TO PERMIT RADIAL MOVEMENT OF THE SEGMENTS IN THE SEAT; WEDGE BLOCK MEANS REMOVABLY SECURED TO THE TABLE ADJACENT THE INNER EDGES THEREOF ADAPTED TO FORCE THE SEGMENTS DURING NORMAL OPERATION RADIALLY OUTWARD AGAINST THE SEAT OUTER EDGE; THE TABLE FURTHER INCLUDING AT LEAST ONE REMOVABLE PLATE MEMBER SECURED TO THE TABLE DEFINING A PORTION OF THE SEAT OUTER EDGE COEXTENSIVE WITH AT LEAST ONE SEGMENT TO PERMIT RADIAL REMOVAL OF THE SEGMENT ON REMOVAL OF THE PLATE. 